1. Field of the Invention
Embodiments of the present invention relate to catalysts and solvent combinations for hydrolysis and simultaneous dehydrations of carbohydrate containing biomass to afford platform chemicals from the carbohydrates and methods for making and using same.
Embodiments of the present invention relate to catalysts and solvent combinations for hydrolysis and simultaneous dehydrations of carbohydrate containing biomass to afford platform chemicals from the carbohydrates and methods for making and using same, where the method includes hydrolysis and simultaneous dehydration of carbohydrates, while providing a facile separation from lignin and lignin fragments and where the method uses a solvent system comprising an aqueous ether solution and optionally an acid.
2. Description of the Related Art
Present technology cannot achieve cyclo-dehydrations of carbohydrates or other naturally occurring polymers in high yield directly without the use of exotic and often expensive solvents such as ionic liquids (Zhang 2007) or by using dipolar aprotic solvents such as DMSO, which cannot be recovered and leaves undesirable impurities in the products (see US2008/0033188 to Dumesic).
Present technology has not recognized the impact of the counter ions in these reactions to enable different products (i.e., 5-hydroxymethyl-2-furfural (5-HMF) or levulinic acid (LA)) to be produced much less to control the amounts and types of impurities co-produced. HCl for example can selectively produce 5-HMF from the C6 carbohydrate polymers, while H2SO4 tends to direct the reaction product to LA at the expense of the intermediate 5-HMF.
Weaker acids than these, such as mono-hydrogen sulfate and phosphoric acid that also have weakly nucleophilic counterions, can also allow the reaction to form mainly 5-HMF without the generation of the chloride cleavage product (2-chloroethoxyethanol) resulting from the reaction of the chloride ion (under acidic conditions) with the solvent dioxane. The neutral but reactive 2-chloroethoxyethanol product must also be separated from the final product mix. However, the undesired byproduct, 2-chloroethoxyethanol, can be minimized by careful control of the conditions. For example, weak acid (type of acid and molarity), high substrate loading, and short reaction time all contribute to reactions in which none of this compound is detected. Conversely, a high chloride content with HCl as the acid, at reasonably higher molarity and especially with added chloride salts (especially LiCl), are conditions where dioxane alone affords a new synthesis of the 2-chloroethoxyethanol in high yield that may be of commercial interest.
For the most part, the trend in the industry to make fuels (e.g., ethanol) and platform chemicals (e.g., glucose and xylose) from biomass resources has been to try to avoid the formation of these cyclo-dehydration products, because they were toxic to the fermentation processes used. They were thus deemed as “undesirable degradations.” On the other hand, the reason carbohydrates are poor fuels is because they contain too many oxygens, literally with every carbon having an oxygen from the equivalent of a mole of hydrate (water).
Thus, there is a need in the art for improved methods for converting biomass into a variety of useful platform chemicals.